Peroxide-initiated crosslinking is practiced widely to improve the mechanical and thermal properties of ethylene-rich polyolefins for power transmission cable applications. Although fast and adequate crosslinking is desired at the vulcanization stage, premature crosslinking (scorch) needs to be avoided as much as possible because it adversely affects the quality of the products. Furthermore, scorch causes gelation and adhesion of polymer gel to the internal surfaces of the extruder, which can result in extruder plugging and this, in turn, in extruder downtime to remove the plugs.
To retard scorch the industry relies extensively on phenolic antioxidants. However, the industry also relies extensively on triallyl isocyanurate as a crosslinking co-agent to improve curing efficiency. This combination of scorch retardant and cure co-agent, while effective at one level, proves to be a difficult balance to achieve and maintain, and leaves space for operational improvement.
JP 4 523 801 B2 discloses an isocyanuric acid compound (Formula 1, an isocyanuric acid/phenol compound) that is used as an antioxidant in polymeric materials.
R represents an allyl group or a 3,5-di-tert-butyl-4-hydroxybenzyl group. This reference teaches the synthesis of the compound and its possible use in polymeric materials to improve the compatibility of the antioxidant with the host polymer and to retard its exudation from the polymer. The reference does not teach the use of this compound in polymeric materials to improve the scorch performance by the synergistic effect of the hindered phenol and the allyl isocyanurate groups. The reference also teaches only a very general composition of polymeric material and an isocyanuric acid/phenol compound. It does not teach a composition of a polymeric material, a peroxide, and an allyl isocyanuric acid/phenol compound.
US 2013/0149645 A1 discloses a chemically amplified negative resist composition used in the field of semiconductor fabrication. The composition comprise an isocyanuric acid with a general structure depicted as Formula 2.
R1, R2 and R3 may be the same or different, at least one of R1, R2 and R3 is a crosslinking group or a monovalent organic group having a reaction site susceptible to crosslinking, and the remaining R groups are a monovalent hydrocarbon group of 1-20 carbon atoms. This general structure is very broad and may include an isocyanuric acid/phenol structure. However, it does not teach this structure in the context of a hybrid scorch retardant/cure co-agent for use in the extrusion of ethylene-based polymers.